Proteins such as pharmaceutically important proteins like hormones and industrially important proteins like enzymes are becoming more widely used. Enzymes are used in several industries including, for example, the starch industry, the dairy industry, and the detergent industry. It is well known in the detergent industry that the use of enzymes, particularly proteolytic enzymes, has created industrial hygiene concerns for detergent factory workers, particularly due to the health risks associated with dustiness of the available enzymes.
Since the introduction of enzymes into the detergent business, many developments in the granulation and coating of enzymes have been offered by the industry.
U.S. Pat. No. 4,106,991 describes an improved formulation of enzyme granules by including within the composition undergoing granulation, finely divided cellulose fibers in an amount of 2-40% w/w based on the dry weight of the whole composition. In addition, this patent describes that waxy substances can be used to coat the particles of the granulate.
U.S. Pat. No. 4,689,297 describes enzyme containing particles which comprise a particulate, water dispersible core which is 150-2,000 microns in its longest dimension, a uniform layer of enzyme around the core particle which amounts to 10%-35% by weight of the weight of the core particle, and a layer of macro-molecular, film-forming, water soluble or dispersible coating agent uniformly surrounding the enzyme layer wherein the combination of enzyme and coating agent is from 25-55% of the weight of the core particle. The core material described in this patent includes clay, a sugar crystal enclosed in layers of corn starch which is coated with a layer of dextrin, agglomerated potato starch, particulate salt, agglomerated trisodium citrate, pan crystallized NaCl flakes, bentonite granules or prills, granules containing bentonite, kaolin and diatomaceous earth or sodium citrate crystals. The film forming material may be a fatty acid ester, an alkoxylated alcohol, a polyvinyl alcohol or an ethoxylated alkylphenol.
U.S. Pat. No. 4,740,469 describes an enzyme granular composition consisting essentially of from 1-35% by weight of an enzyme and from 0.5-30% by weight of a synthetic fibrous material having an average length of from 100-500 micron and a fineness in the range of from 0.05-0.7 denier, with the balance being an extender or filler. The granular composition may further comprise a molten waxy material, such as polyethylene glycol, and optionally a colorant such as titanium dioxide.
U.S. Pat. No. 5,324,649 describes enzyme-containing granules having a core, an enzyme layer and an outer coating layer. The enzyme layer and, optionally, the core and outer coating layer contain a vinyl polymer.
WO 91/09941 describes an enzyme containing preparation whereby at least 50% of the enzymatic activity is present in the preparation as enzyme crystals. The preparation can be either a slurry or a granulate.
WO 97/12958 discloses a microgranular enzyme composition. The granules are made by fluid-bed agglomeration which results in granules with numerous carrier or seed particles coated with enzyme and bound together by a binder.
Two of the methods known for preparing granulated enzymes in fluid-bed coaters include fluid-bed agglomeration and fluid-bed spray-coating. In fluid-bed agglomeration, one or more enzymes and a binder are sprayed on to fine powdery carrier solids, which are built up in size by agglomerating together carrier particles. In these agglomerates, the binder and enzyme serve to bridge multiple carrier particles into granules of irregular size and shape. In fluid-bed spray-coating, enzyme can be layered onto uniform core particles together with an optional binder.
It would be desirable to produce enzyme granules with improved stability, particularly in bleach-containing detergents at high humidity and temperature. Current fluid-bed spray-coated enzyme granules contain the enzyme in a relatively thin layer near the surface of the granule. This geometry renders the enzyme more vulnerable to being chipped off of the granule in a concentrated layer during handling and conveying operations, increasing the likelihood and levels of airborne enzyme aerosols in the working environment. This geometry also makes the enzyme more vulnerable to attack by penetrating moisture and inactivating substances.
However, even in light of these developments offered by the industry (as described above) there is a continuing need for low-dust enzyme granules which have additional beneficial characteristics. Additional beneficial characteristics needed in the enzyme granulation industry are low-residue granule formulations (where low residue is defined as a reduced tendency to leave noticeable undissolved residues on clothes or other material), and improved stability during storage in, for example, bleach-containing detergent formulas, for example, those containing peroxygen bleaches such as sodium perborate or sodium percarbonate. Accomplishing all these desired characteristics simultaneously is a particularly challenging task since, for example, many delayed release or low-dust agents such as fibrous cellulose or kaolin leave behind insoluble residues.
As such, there is a need for, for example, a detergent enzyme granule which is simultaneously non-dusting, stable when stored in detergents, and easy to manufacture in a controlled size distribution. Granules of a controlled size distribution are desirable in order to impart good flowability properties for handling and blending into detergents, and to resist segregation and settling once formulated into detergents. A controlled particle size distribution and uniform shape of particles are also important contributors to achieving a low dust granule.
Therefore, it is an object of the present invention to provide low-dust, low residue, highly soluble enzyme granules having increased stability particularly in bleach-containing detergents. It is another object of the present invention to provide processes which afford the formation of such improved granules.